The utilization of water which contains certain inorganic impurities, and the production and processing of crude oil water mixtures containing such impurities, is plagued by the precipitation of these impurities with subsequent scale formation. In the case of water which contains these contaminants the harmful effects of scale formation are generally confined to the reduction of the capacity or bore of receptacles and conduits employed to store and convey the contaminated water. In the case of conduits, the impedance of flow is an obvious consequence. However, a number of equally consequential problems are realized in specific utilizations of contaminated water. For example, scale formed upon the surfaces of storage vessels and conveying lines for process water may break loose and these large masses of deposit are entrained in and conveyed by the process water to damage and clog equipment through which the water is passed, e.g., tubes, valves, filters and screens. In addition, these crystalline deposits may appear in, and detract from, the final product which is derived from the process, e.g., paper formed from an aqueous suspension of pulp. Furthermore, when the contaminated water is involved in a heat exchange process, as either the "hot" or "cold" medium, scale will be formed upon the heat exchange surfaces which are contacted by the water. Such scale formation forms an insulating or thermal opacifying barrier which impairs heat transfer efficiency as well as impeding flow through the system.
While calcium sulfate and calcium carbonate are primary contributors to scale formation, other salts of alkaline-earth metals and the aluminum silicates are also offenders, e.g., magnesium carbonate, barium sulfate, the aluminum silicates provided by silts of the bentonitic, illitic, kaolinitic, etc., types.
Many other industrial waters, while not being scale forming, tend to be corrosive. Such waters, when in contact with a variety of metal surfaces such as ferrous metals, aluminum, copper and its alloys, tend to corrode one or more of such metals or alloys. A variety of compounds have been suggested to alleviate these problems. Such materials are low molecular weight polyacrylic acid polymers. Corrosive waters of this type are usually acidic in pH and are commonly found in closed recirculating systems.
Numerous compounds have been added to these industrial waters in an attempt to prevent or reduce scale and corrosion. One such class of materials are the well known organophosphonates which are illustrated by the compounds hydroxyethylidene diphosphonic acid (HEDP) and phosphonobutane tricarboxylic acid (PBTC). Another group of active scale and corrosion inhibitors are the monosodium phosphinicobis (succinic acids) which are described in U.S. Pat. No. 4,088,678.
The present invention relates to preventing scale and corrosion of metal surfaces in contact with scale forming or corrosive industrial process waters with low molecular weight acrylamide polymers, acrylic acid polymers and co-polymers of acrylic acid with acrylamide which have been modified to incorporate within their structure C.sub.2 -C.sub.6 amidoalkylphosphinic acid groups and the alkali metal, ammonia and amine salts thereof.